This invention relates to adducts of a polyhydric alcohol and a monoepoxide and to a process for preparing the same. In a specific aspect, the invention relates to a process for the preparation of an adduct of a polyhydric alcohol and an aromatic monoepoxide and to curable coating compositions containing such adducts. In another aspect, the invention relates to a process for coating a surface by applying said coating composition.
Resinous polyhydric polyether adducts are well-known useful materials, for example, in the solvent, foam and coating industries. In general, they offer good properties and are more chemically resistant than polyhydric polyester resins in coatings. For example, GB-A-1,531,778 describes preparation of polyetheralcohols used in the preparation of polyurethane foam by the addition of an epoxide (ethylene oxide, propylene oxide) to an at least divalent alcohol, such as glycerol or pentaerythritol, and polyethylene glycol in the presence of alkaline catalysts.
Other examples for the preparation of these adducts are found in U.S. Pat. No. 4,282,387 and U.S. Pat. No. 4,326,047. U.S. Pat. No. 4,282,387 describes a reaction of a monoepoxide (propylene oxide) and at least one active hydrogen containing compound catalyzed by a calcium, barium or strontium containing catalyst; U.S. Pat. No. 4,326,047 describes preparation of polyether hydroxyl-containing compounds (using propylene oxide) in the presence of a solid calcium naphthenate.
However, none of the above references addresses the desirability of preparing a monoepoxide-polyhydric alcohol adduct having a relatively low viscosity (i.e., free of highly polymerized compounds) while containing a lesser amount of unreacted starting materials, a product with a narrow molecular weight distribution. In particular, these processes do not provide adducts of an aromatic monoepoxide and a polyhydric alcohol.
Therefore, it is an object of the invention to provide for adducts of aromatic monoepoxides and polyhydric alcohols. It is another object of the invention to provide for a process to obtain such adducts with a narrow molecular weight distribution.